The photo-oxidation of aliphatic alcohols as monolayers on aqueous solutions of 1,1′-dimethyl-4,4′-bipyridylium (paraquat) dichloride

Abstract

The oxidation of monomolecular films of primary and secondary long-chain aliphatic alcohols on aqueous solutions of paraquat dichicride when irradiated with light of 254 nm wavelength has been studied kinetically. The primary alcohols (C₁₄, C₁₅, C₂₀, C₂₄) are oxidised smoothly and completely and obey pseudo-zero-order kinetics. The rate of reaction is related to the concentration of chloride ions at the interface. Electronic energy transfer from molecules excited in the bulk solution to those at the interface was shown to be important. The secondary alcohols investigated (cyclododecanol, hexadecan-2-ol, octadecan-2-ol) behaved differently, in that oxidation only proceeds to 30–70% completion. Mixed film experiments with octadecan-2-ol and octadecan-2-one have been performed.